1. Field of the Invention
The present invention relates generally to plugs and fasteners and, more particularly, to plugs and fasteners requiring a special tool for easy removal without damage.
2. Description of the Prior Art
Tank drain plugs, such as are found on gasoline tanks of trucks and stationary storage tanks, are generally insertable and removable by use of standard tools such as wrenches. However, the increases in petroleum prices have made theft by removing the drain plug and draining a tank of its contents a not uncommon occurrence. Thus it is a problem to deter theft by use of a tank drain plug which cannot be easily removed with commonly available tools, which is of rugged, durable, and inexpensive construction, and which may be easily inserted and removed without damage with a proper tool.
Frequently fasteners, such as are used to assemble partitions in lavatories, are desirably not easily removed, and use of the one-way ramp head screw is common. But, such a screw cannot be easily removed, short of drilling, even with special tools. Thus it is a problem to provide fasteners which may be easily removed only with special tools and without damage to the fastener.